Electrocaloric effects in both ferroelectric and nonferroelectric dielectric media have previously been reported in the literature. A. Kikuchi, et al, J. Phys. Soc. Japan 19, 1497 (1964) and E. Hegenbarth, Phys. Stat. Sol. 8, 59 (1965) describe the electrocaloric effect in a single crystal ferroelectric, and E. Hegenbarth, Cryogenics 1, 242 (1961) describes it in a ceramic ferroelectric, and I. W. Shepherd, J. Phys. Chem. Solids 28, 2027 (1967) describes it as observed in the non-ferroelectric material KCl containing orientable OH.sup.- defects. The terminology and technology as disclosed by said latter reference are incorporated herein by reference for the purpose of the practice of the present invention.
The existence of an electrocaloric effect suggests that it might be possible to construct a refrigerator based on this effect. However, the capacity of a refrigerator which might be constructed using the electrocaloric effect in ferroelectric materials is severely limited by the saturation of the temperature dependent polarization at high fields and by the relatively low Debye temperatures, .theta..sub.D, of ferroelectric crystals. The maximum .DELTA.T around 10K which has been reported to date in a ferroelectric medium is the 0.28 degree electrocaloric effect at 11.5.degree. K. in single crystal SrTiO.sub.3 described by Kikuchi, et al (op. cit.). It appears that the magnitude of this .DELTA.T might be increased by about a factor of 4 by resort to higher electric fields. A substantially greater increase in .DELTA.T could be obtained were it possible to use a ferroelectric with a Debye temperature .theta..sub.D significantly greater than that of SrTiO.sub.3, but this does not seem to be possible; the .theta..sub.D of ferroelectrics are always suppressed by the soft phonon modes which are responsible for their ferroelectric behavior. No successful attempt to make a refrigerator based on the electrocaloric effect in ferroelectrics has been reported.
The maximum electrocaloric effect observed by Shepherd (op. cit.) in KCl crystals containing OH.sup.- defects was between 0.3K and 1.3K. This was produced by the adiabatic orientation and randomization of the electric dipoles of the OH.sup.- defects in an applied electric field when the KCl was formed into a capacitor and carefully isolated thermally within a liquid He cryostat. The physical principles of this effect were discussed by Shepherd who likened them to magnetic cooling. However, no attempt to use this effect in KCl or similar materials to construct a dielectric refrigerator operating over any temperature range has been reported.